Field of the Invention
The present invention is related to a control circuit, and more particularly to a control circuit which comprises both feedback paths and can be widely applied to various controller-area-network bus application systems.
Description of the Prior Art
As known, controller area network (CAN) is a kind of specification established in early 1990's, got standardized as ISO 11898-1 in 1993, and widely used in all kinds of vehicles and electronic devices later on. In general, controller area network includes a serial bus, which provides high security level and efficient real-time control. Also, it is able to ensure debugging and priority determining mechanism, thereby making transmissions for internet messages much more reliable and efficient than ever. From this point of view, it is believed that the controller area network nowadays not only has highly flexible adjustment ability which can accommodate more station numbers in existed internet without modifying its software and/or hardware, but also enhances network upgrading conveniences since its data transmission path need not build upon certain specific standard stations.
Please refer to FIG. 1, which is a schematic drawing of a conventional controller area network bus, wherein two stations, i.e. a station 21 and a station 23 are disposed in the controller area network and are individually connected to a common bus 30 through each of the can-transceivers 11. A high-level output CANH and a low-level output CANL are utilized to provide a differential signal so as to achieve transmitting signals. In the digital logic design nowadays, for example as shown in FIG. 2, when the high-level output CANH and the low-level output CANL are both 2.5V, then the digital signal output will be “1”. On the other hand, when the high-level output CANH is raised to 3.5V and the low-level output CANL is lowered to 1.5V, then the digital signal output will become “0”. For maintaining a DC stability of the high-level output CANH and the low-level output CANL, a prior art such as U.S. Pat. No. 6,922,073 has disclosed a certain circuit diagram to balance its bus output voltages, in which an output circuit and a preamplifier are needed to comply with a single-path control circuit so as to control a voltage source of the preamplifier. By such arrangements, an effective resistance Ron at one end of the circuit will be equal to another effective resistance at the other end, whereby the DC stability control can be achieved.
However, it shall be noticed that in order to achieve the DC stability control, a great number of electronic components must be used no matter from the systematic design or IC chip design point of view. In addition, the circuit complexity would be accordingly increased as well. Under such circumstances, the production cost for the circuit and numbers of components must be dramatically raised too, which induces severe budget issues.
On account of all, it should be apparent and obvious that there is indeed an urgent need for the professionals in the field for a novel control circuit to be developed so as to solve the above-mentioned problems occurring in the prior design.